Evanescent wave immunoassay system

Abstract

Apparatus for assaying a fluid sample with radiation capable of exciting fluorescence in fluorescent material comprises a totally internally reflecting, unitary elongated substrate transmissive to both the excitation radiation and to the fluorescence. The fluorescent material includes at least a moiety of an antibody-antigen complex that includes a tag that will provide the fluorescence when excited by an evanescent wave generated by the excitation radiation. The substrate includes an elongated fiber and an integral lens formed to guide the optical radiation into the fiber within the bounds of a critical angle to assure total internal reflectance. A hollow elongated enclosure is disposed concentrically about and spaced from the fiber so as to provide an interspace of capillary dimensions. A test implement supports the elongated substrate, has a reservoir for receiving a fluid sample to be assayed, and is selectively movable to an operative position whereat the fluid sample is caused to flow onto the fiber and, by capillary action, into the interspace between the fiber and the enclosure. The apparatus further includes a source of the excitation radiation, refractive element for focusing the radiation toward the lens, detector for detecting fluorescence radiation emitted from an end of the fiber responsively to the excitation radiation, and optics frame for mounting all components in fixed relation to the lens for introducing the excitation radiation into the lens within the critical angle.